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"The unit operation of liquid-liquid extraction has developed enormously in the last 20 years and is now recognized as one of the most important techniques for the physical separation and refining of industrial liquids. For years the conventional apparatus used for liquid-liquid extraction has been towers employing countercurrent flow of the liquids and equipped with various means to increase the interfacial area.

The countercurrent column consists of a tower through which flows a continuous phase while countercurrent to this flow is a stream of droplets (the dispersed phase). Provision is made for dispersing one phase with a settling region at each end of the tower. This arrangement corresponds to the single spray tower in absorption but in practice such a simple apparatus has a very low efficiency due to incomplete mixing and coalescing of the original droplets.

A recent design for the improvement of liquid-liquid extraction equipment involves a column utilizing countercurrent flow, mechanical agitation, and baffled settling zones. In one case, the column is fitted with sieve plates that may be moved up and down relative to the liquid producing the agitation, while the liquids flow countercurrently through the plates. Settling takes place during the pauses between the strokes. The operation and construction or this column can be simplified by using stationary plates and agitating by imparting a reciprocating motion to the liquids relative to the plates. Another possible design is a column which consists of a number of compartments formed by a series of stator rings, with a rotating disc centered in each compartment and supported by a rotating shaft. This apparatus has been proved to be highly efficient, simple, and cheap to operate, and easy to maintain.

The purpose of this thesis was to design a liquid-liquid extraction system containing (1) a pulse extraction column and (2) a rotating-disc contactor column for non-hazardous, simulated, nuclear fuel processing. The system was designed such that the two columns may be operated (1) separately, (2) as a countercurrent system, and (3) as a multiple contact system"--Introduction, pages 1-2.